The present invention relates to wall structures that may be fire rated and/or accommodate seismic shifts or settlings of the building.
In building construction, conventional wall fabrication techniques employ wooden materials such as headers and footers as well as wooden vertical studs placed between the headers and footers to form a wall frame. Unfortunately, traditional wooden wall constructions suffer from several drawbacks including the excessive time to erect the wall structure, high material costs, and heavy weight.
In certain situations, metallic framing structures are now used in buildings due to its light weight, ease of erecting the wall structure and low expense. Nonetheless, these metallic wall frames suffer from other deficiencies. In particular, the metallic framing structures are fabricated similar to a wooden framing structure in that there are a plurality of vertical studs held between a header and footer. The header and footer are secured to the ceiling and floor to stabilize the wall structure. Unfortunately, during building fabrication, the distance between the ceiling and floor may vary. By way of example and not limitation, metallic framing structures may be implemented in high rise or mini rise structures. Each floor is comprised of a poured reinforced concrete. Variations between each floor (i.e., ceiling to floor distances) may be up to about six inches (6″). When the metallic framing structures are erected under these conditions, the metallic vertical studs must be cut to fit the ceiling to floor height or a plurality of different vertical stud lengths must be stored to fit the ceiling to floor height. Solutions have been presented to eliminate the need to cut to fit the vertical stud or store a variety of vertical stud lengths. One such solution is disclosed in U.S. Pat. No. 7,223,043 (hereinafter '043 Patent) issued to William Andrews. The '043 Patent discloses a metal stud member (i.e., vertical stud) and a metal plate member (i.e., header or footer) which interlock with each other via a simple twist and lock manipulation. Additionally, the vertical stud members may be telescopic in nature. The telescopic feature of the vertical studs accommodate the ceiling to floor variations that exist not only in high rise or mini rise structures but also in other types of structures. The installer attaches an upper metal plate member to the ceiling and a lower metal plate member to the floor in alignment with the upper metal plate member. The metal stud members are disposed between the upper and lower metal plate members and extended via the telescopic feature to the precise distance between the ceiling and floor (i.e., upper and lower metal plate members). The solution provided in the '043 Patent allows the installer to precisely fit the vertical stud member to the ceiling to floor height without cutting the metallic vertical stud member to length or storing various lengths of vertical stud members.
The metallic wall frame fabricated from the metallic header, metallic footer and metallic vertical stud members address the variations in ceiling to floor height during installation. However, other factors in future changes in the ceiling to floor height must also be considered. By way of example and not limitation, ceiling to floor height variations may occur during seismic shifts, fire due to thermal expansion, changes due to normal ambient temperature changes, and settling of the building during and after construction of the building. In most buildings, after the metallic wall frame is erected, drywall is attached to the metallic wall frame. To this end, a plurality of screws are screwed through the drywall and into the metallic vertical studs. Unfortunately, these screws may bind the inner and outer metallic vertical members that allow the metallic vertical stud to be telescopic. In essence, the screws lock the length or height of the vertical stud member. During seismic shifts, the ceiling to floor height may increase and decrease during the seismic shift. If the metallic vertical studs are no longer telescopic but fixed due to the screws, then these vertical studs may be crushed or pulled apart during the seismic shift. During fire, the building (i.e., floors, ceilings and wall structures) may experience heat that causes thermal expansion. The thermal expansion may cause the ceiling to floor height to increase or decrease. If the metallic vertical studs are not telescopic but fixed due to the screws, then in this situation also, the metallic vertical studs may be crushed or pulled apart due to the thermal expansion of the various parts of the building. Moreover, during construction and after completion, the building may settle into the ground thereby causing the ceiling to floor height to slowly change over a period of time. If the screws affixed to the metallic vertical studs do not allow the metallic vertical studs to be telescopic, then the settling of the building may cause the metallic vertical studs to rupture (i.e., pull apart) or be crushed under the weight of the building.
Solutions have been provided that address the changing nature of the ceiling to floor height distance. By way of example and not limitation, U.S. Pat. No. RE 39,462 (hereinafter '462 Patent) illustrates a vertically slotted header to allow for spatial variations in distance between a ceiling and floor. As shown in the '462 Patent, a header is attached to a vertical stud. The header is allowed to traverse vertically with respect to the vertical stud through a slot in a sidewall of the header. This type of vertical displacement is typically used for achieving a fire rating for the wall structure. In a fire, the distance between the ceiling and floor may change due to the thermal expansion of the wall structure. The allowable vertical displacement maintains the wall structure in tact despite different coefficients of thermal expansion of the various materials of the wall structure.
Unfortunately, the device of the '462 Patent suffers from various drawbacks. First, the amount of vertical displacement is limited by a length of the slot. Moreover, the lateral position of the stud with respect to the header is limited by the placement of the slot. The lateral position of the stud cannot be minutely adjusted based on the circumstances. The stud must be aligned to the slot. Additionally, the header shown in the '462 Patent is generally weak due to the plurality of unnecessary slots that are formed in the sidewalls of the header. If the header is subjected to a vertical load, then the header may be likely to deform at the location of the slots due to stress concentrations and the like. Moreover, the screw that attaches the sidewall of the header to the sidewall of the vertical stud is located at the very top of the wall frame and also close to the ceiling. As such, the construction worker has a very small area to work with in screwing the screw into the metallic header and vertical stud.
Another solution is disclosed in U.S. patent application Ser. No. 11/483,791 (hereinafter '791 Application), the entire contents of which is expressly incorporated herein by reference. In the '791 Application, the telescopic feature of the metallic vertical stud is retained despite the drywall being screwed into the vertical stud member. This is accomplished by slotting one of the telescoping members of the vertical stud member such that the screw attaching the drywall to the wall frame is secured only to one of the telescoping members and not both. Unfortunately, the length of the slot is not very long. It allows for only approximately a three inch (3″) vertical deflection, a small amount. Additionally, since the drywall is placed over the plurality of vertical stud members, the location of the slot cannot be seen. As such, the installer may inadvertently screw the screw into both of the telescoping members that make up the telescopic vertical stud member. Accordingly, there is a need for a telescopic vertical stud member that allows for infinite vertical deflection and is not subject to installation error.